The inventor of this application and others have proceeded research on a technique for measuring thermal radiation using infrared light and the measurement technique has been disclosed (Non-Patent Document 1). The inventor of this application and others have disclosed a so-called passive infrared light condensing apparatus which combines a solid immersion lens and an atomic force microscopy (AFM) (Patent Document 1). However, the above techniques are each mainly based on the condition that an object to be measured is a solid material.